Astronomy Specialist


$929.00 AUD
SKU: BA2956510V

Baader Planetarium



The Baader 2" Cool-Ceramic Safety Herschel Prism Mark II is a 2" diagonal designed to give uncompromising white light views of the solar photosphere. Both Visual and Photographic versions are available with neutral density filters of varying strengths depending on the application. No additional front-mounted rejection filter or solar film is needed with standard refractors to safely observe the sun when using the built-in ND 3.0 filter.

Warning: Herschel Prisms cannot be used with Petzval telescopes or other designs that have glass in the optical path near the focal point. As long as the light has not been concentrated at the focal point, the heat input is not great enough to cause damage to your equipment.

Herschel prisms must always be operated with additional light attenuation filters. Every Herschel wedge needs additional neutral density filters since the reflected energy of the first surface prism (4.6%) still is a factor of 1000 too large for the human eye. All Baader Solar Diagonals are delivered with a pre-mounted ND 3.0 Baader precision 2" light reduction filter. The photographic version includes even more ND filters for selective light attenuation when using cameras and high magnifications.

The new Mark II Herschel Prism includes an integrated rotation mechanism for polarizing filters, allow stepless brightness adjustment with the addition of a single polarizing filter (sold separately). Since the Herschel Prism emits a beam of polarized light, a double polarizer is not necessary. 



Comparison between ordinary white light on the left and with the included 7.5nm Solar Continuum filter on the right.


Both versions include the new 7.5nm Solar Continuum filter with a narrow bandpass centred around 540nm, where telescope optics are their sharpest. This combination gives the highest quality white light views possible. In addition, a new 3-point adjustment system is pre-set from the factory to give optimal performance. On the telescope-side is a 2" nosepiece with safety kerfs as well as an S58 dovetail, making the unit compatible with Diamond Steeltrack adapters.



Advantages of the Safety Cool-Ceramic Herschel Prism

  • Space technology: a multiple staggered light trap made of heat protection sheets and heat-absorbing special ceramics as the end of the light trap - similar to heat tiles on the space shuttle - absorbs the radiant heat without heating the surroundings too much. The prism also remains temperature-stable for a long time.
  • Enclosed housing: no risk of glare or fire from the emitted sunlight, observation is possible without danger.
  • Solar finder: the ceramic plate also acts as a screen for the sunlight beam. Aiming the telescope at the sun becomes very easy.
  • ClickLock Clamp: included is a 2" ClickLock with 15° of rotation, allowing you to clamp every eyepiece and accessory securely, even in winter with thick gloves.
  • Short overall length: the unit can be shortened by 30mm for use with imaging cameras or binoviewers with the optional Diamond Steeltrack T2 adapter BA2957202 or M48 adapter BA2957204.
  • Filter holder:  with the integrated rotatable filter holder, all necessary filters are firmly installed in the housing so there is no danger when changing eyepieces.
  • Brightness adjustment for photography: to let enough light through for photography at high magnifications, the pre-installed ND3 filter can be replaced by weaker filters (sold separately, or included with the photo version).

The Herschel wedge is based on the principle of using only a small part (4.6%) of the incident light for the actual observation. This 4.6% is reduced again by a factor of 1000 to a harmless level by the ND 3.0 neutral density filter, which is installed as standard in both versions. The unequally larger, high-energy part of the light falls through the housing and forms a focal point in the air outside. Even far behind this focal point, this light concentration would still be irritatingly bright and dangerous if an inexperienced observer were to accidentally (or wantonly) look into the output beam. Therefore, Baader Herschel prisms have been using light traps for years to eliminate this risk. With the closed light trap with Cool-Ceramic protection plate, observing the sun with a Herschel prism is possible without danger for private persons as well as for public institutions and schools.


Optical design Herschel Prism
Reflection surface First surface reflection
Image orientation Erect image, mirror-inverted
Phantom Coating Group
Solar wavelength
White light
Clamping system
Housing Die-cast aluminium, milled, matte black anodized, pearl white textured finish
Connection telescope side
2" nosepiece, M48 x 0.75 female, S58 dovetail
Connection eyepiece side
2" clamp, S58 dovetail
Weight TBD
SKU BA2956510V (Visual), BA2956510P (Photographic)





  • Baader Herschel Prism Mark II with 2" Clicklock
  • Hardcase
  • Baader 7.5nm Solar Continuum filter 2"
  • Baader Neutral Density filter ND 3.0 (T=0.1%)




  • Baader Herschel Prism Mark II with 2" Clicklock
  • Hardcase
  • Baader 7.5nm Solar Continuum filter 2"
  • Baader Neutral Density filter ND 3.0 (T=0.1%)
  • Baader Neutral Density filter ND 1.8 (T=1.5%)
  • Baader Neutral Density filter ND 0.9 (T=12.5%)
  • Baader Neutral Density filter ND 0.6 (T=25%)

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  • Visual
  • Photographic

Optical design

Image circle

Focal ratio


Focal length

Optical thickness



Colour or Mono

Pixel size

Sensor dimensions


Sensor diagonal

Quantum efficiency

Read noise

Fullwell capacity

Bit depth


Camera backfocus

Filter size

Filter size

Bandpass (FWHM)

Bandpass (FWHM)

Glass thickness

Mount type

Payload capacity

Latitude range

Dovetail saddle

Slew speed


Periodic error correction

Counterweight shaft

Azimuth adjustment range

Internal diameter

Illuminated diameter

Compatible telescope external diameter





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